Improved process of roasting- auriferous stjlphitrets



waited $131325 than Gtihiirc.

\VIL LIAM BRUCKNEROF CENTRAL, COLORADO TERRITORY.

' Letters Patent No. 92,009, dated Jtme 29, 1869.

To all whom it may concern Be it known that I, WILLIAM Bntioklvnn, of Gentral, Gilpin county, Colorado Territory, have invented certain new and useful Improvements in the Process for Roasting Aurit'erous Sulphurets; and I do hereby declare the following description and accompanying drawings are sufiicientto. enable any person skilled in the art or science to which it most nearly appertains, to make and use my said invention or improvements, without further invention or experiment.

The nature of my invention and improvements consists in the use, in a particular manner, and for special purposes, to be herein described, of common salt, or other substance yielding chlorine and lime, in the roasting of aurii'erous sulphurets, to prepare them for the process of amalgamation.

Experience has shown, that by the roasting-processes heretofore in use, not more than from fifty to sixty per cent.,0f the gold contained in these ores has been obtained from them by amalgamation, and that proportion only from the best sort of iron sulphurets, while from the more refractory ores, such as those of Colorado, and particularly those that have not been exposed to the decomposing-action of the atmosphere, often not more than from twenty-five to thirty per cent. of the gold has been obtained.

At the same time there has been agreat lossor .waste of quicksilver, from its becoming coated, or converted into calomel, or floured, in which state it has no aflinity for gold, and does not combine with it. Now, the low yield of gold, as above stated, I have found to be owing to two causes: first, a coating formrd on the gold in the ordinary process of roasting theore, and second, the destruction of the amalgamating-capacity of the quicksilver by the sulphates, chlorides, or other products of the roasting-process.

For both these causes, my'iinprovement is found to be an efficient remedy, and so complete, that by using it, nearly all the gold may be extracted from the most reii'actory ores, or at least eighty or ninety per cent. thereof, by amalgamation.

I will now describe my improved process. The auriferous sulphurets are to be finely pulverizcd and the roasting-furnace charged. The ore should be constantly stirred, and the heat raised until the sulphur begins to burn and escape througlrthc chimney,

but should then beraised no higher till the sulphur isv burned oft. After that has been effected, a strong heat should be put on, and charcoal or sawdust may be advantageously added, to deprive the base metals, commonly contained in the ore, of the last atoms of sulphur or sulphur-acid.

This operation is called dead-roasting, and all the gold is now set free, except that it will be found to be more or less coated, according to the amount of cop- 'per, lead, or other base metal containedin the ore.

susceptible of amalgamation.

For this process or operation, about half an hour is suflicicnt.

It the ore treated as above was one of the purer I sort of iron sulphurets, containing no lead,'copper, or other such base metal, or only very small proportions thereof, the ore is now ready for amalgamation, no considerable amount of the chlorides of these metals having been formed, to injure the quicksilver by converting it into calomel, or causing it to flour.

But if the base metals above referred to were present in the cm in anyconsiderable quantities, which may be ascertained by an examination of the particles of gold before the application of salt, then carbonate of lime, burnt lime, or some equivalent, must be added, to prevent the chlorides of these metals, formed by the use and decomposition of the salt, from acting upon and injuring the quicksilver, as already described.

By this means the lime, or a portion of it, is converted into chloride of lime, and the metals aforesaid into oxides, which have no injurious effect upon the quicksilver.

No more lime should be used than what may be required for the decomposition of the chlorides. From one to three per cent.I have generally found to be sutlicient; but if a proper testindicates still the presence of the chloride of copper, or of any other base metal, more lime must be added, till all traces oft-hese chlorides are removed. From half an hour to one hour is commonly sufiicient for this part of the process. 1

I also contemplate the application of chlorine-gas, previously prepared, in place of the compound chloride of sodium.

Having thus described my improved process, it is to be understood that I do not claim as new the use of salt and lime in roasting ores; but" \Vhat I do claim, and desire to secure by Letters Patent, is-

Theme and application of these materials, in a particular manner, and for special purposes, substantially as set forth in the foregoing specification.

WILLIAM BRUGKNER.

Witnesses J. Dnlvnls, Jr., WM. Dnmus. 

